Preheat oven to 350 degrees. Lightly grease a jelly roll pan.
In a large bowl. beat the eggs until they are a lemon color and thick. Add the vanilla, sugar and softened butter to the bowl, beat until well combined.
Combine the flour and baking powder together in a medium bowl. Add the flour mixture in thirds to the batter mixture alternately with the milk. Example: (Add 1/3 cup of the flour, beat until just incorporated. Add half of the milk, beat until just incorporated. Add another third of flour, mix until just incorporated. Add the remaining milk, mix until just incorporated and finally the last 1/3 of the flour. Mixing until just incorporated.
Place the batter in the prepared jelly roll pan. Bake at 350 degrees for 25 - 30 minutes until top is golden and a toothpick inserted comes out clean.
Place the cake on a cooling rack. While the cake is hot, place dollops of peanut butter over the entire surface of the cake. Allow to sit about ten minutes so the peanut butter warms up and is easier to spread over the cake. Use an icing spatula to spread the warmed up peanut butter over the entire cake. Allow the cake to cool completely before frosting with Chocolate frosting.